Monkey 'IQ test' hints at intelligent human ancestor

作者：冀欠 发布时间：2019-03-08 12:12:02

By Ewen Callaway Human intelligence may not be so human after all. New research on monkeys finds that individual animals perform consistently on numerous different tests of intelligence – a hallmark of human IQ and, perhaps, an indication that human intellect has a very ancient history. No doubt, the human brain has bulged in the six million or so years since our species last shared a common ancestor with chimpanzees, offering more cognitive prowess compared to our closest relatives. But traces of human intelligence, such as a sense of numbers, or the ability to use tools, lurk in a wide range of animals, particularly in other primates. Less clear, though, is whether animals possess the same kind of general intelligence as humans: where performance on one facet, say verbal, strongly predicts performance on other tests of intelligence like working memory. “We were essentially looking for evidence of a general intelligence factor – something that would be an evolutionary homologue of what we see in humans,” says Konika Banerjee, a psychologist at Harvard University who led the new study along with colleague Marc Hauser. Working with 22 cotton-top tamarins (Saguinus Oedipus), the researchers tested all the monkeys on a wide range of cognitive tasks, 11 in total. “What we did here was, very crudely, create a monkey IQ test,” Banerjee says. In most tasks, the monkeys ended up in clear-cut groupings – above average, average, and below average. For instance, in one test, animals had to reach around a plastic barrier to obtain a raisin placed right in front of them, but behind the barrier. The smartest monkeys quickly figured out the trick, another group went straight for the raisin before realizing a reach-around was needed, while the dunces never seem to it figure out, Banerjee says. There was less of a spread in a test of numerical discrimination, when monkeys had to pick between two dishes, one with three treats another with four. Most monkeys consistently picked the dish with four treats. Banerjee’s team ranked the 22 monkeys across all 11 tasks and found that the same animals tended to perform similarly well across all the tests. When her team calculated an IQ score for each monkey, the smarter monkey bested the less intelligent monkey two-thirds of the time for any given test. “This is a difficult study to undertake, and this team should be commended for doing it so well,” says Robert Deaner, a psychologist at Grand Valley State University in Allendale, Michigan. He says the new work “really strengthens the argument” that general intelligence has a long evolutionary history. Journal reference: PLoS ONE (in press) More on these topics: